Assertion (A) : In the modern periodic table period indicates the
value of azimuthal quantum number.
Reason (R ): Each period begins with the filling of new shell.

Options

A. If both Assertion (A) and (R ) are correct and Reason (R ) is the
correct explanation of Assertion (A).
B. If both (A) and (R ) are correct but (R ) is not the correct explanation
for (A).
C. If (A) is correct but (R ) is not correct.
D. If (A) is incorrect and (R ) is correct

Explanation

To solve the question regarding the assertion and reason statements about the modern periodic table, we will analyze each statement step by step.

### Step 1: Analyze the Assertion (A)
The assertion states: "In the modern periodic table, period indicates the value of azimuthal quantum number."

- The azimuthal quantum number (denoted as 'l') determines the shape of the orbital and is associated with the subshells (s, p, d, f).
- In the modern periodic table, the period number corresponds to the principal quantum number (n), which indicates the energy level of the outermost shell of electrons, not the azimuthal quantum number.
- Therefore, the assertion is **incorrect**.

### Step 2: Analyze the Reason (R)
The reason states: "Each period begins with the filling of a new shell."

- Each period in the periodic table corresponds to a new principal energy level (n).
- The first period starts with the filling of the 1s subshell, the second period starts with the filling of the 2s subshell, and so on.
- This means that each successive period indeed begins with the filling of a new electron shell.
- Therefore, the reason is **correct**.

### Conclusion
- The assertion is incorrect, while the reason is correct.

Thus, the final answer is that the assertion is incorrect and the reason is correct.

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